Species Limits in Antbirds: The Thamnophilus Punctatus Complex Continued

Abstract

In a previous study (Isler et al. 1997) we examined species limits in the Thamnophilus punctatus complex of the Neotropics. We recommended that six taxa be considered species, but were unable to make recommendations regarding two morphologically distinct and geographically restricted taxa, leucogaster and huallagae, due to the lack of vocal recordings which were essential to our methodology. Analysis of newly obtained recordings has found that vocal differences support the separation at the species level of leucogaster and huallagae from five of the six species in the complex (T. atrinucha, T. stictocephalus, T. sticturus, T. pelzelni, and T. ambiguus). However, leucogaster and huallagae could not be distinguished vocally from each other nor from nominate punctatus to an extent that supported species status, and they are retained as subspecies under our recommended guidelines (Isler et al. 1998, 1999). The Thamnophilus punctatus complex affords an interesting opportunity for future molecular studies that compare the genetic distances among populations that have differentiated vocally and those that have not. The question of species status of leucogaster and huallagae is pressing because the ranges of both taxa are limited to sub-Andean basins in northwestern Peru and southwestern Ecuador that increasingly are under cultivation.

Sexually Selected Traits Predict Patterns of Species Richness in a Diverse Clade of Suboscine Birds

“…Because our analyses were focused on among-taxa variation, we averaged data for each taxon across all individuals and locations (mean ‫ע‬ SD songs per species: 3.4 ‫ע‬ 2.4, range: 2-11; individuals per species: 1.65 ‫ע‬ 1.17, range: 1-5). These samples are adequate for the calculation of genus means, especially as antbird songs are more or less genetically determined and characterized by high stereotypy and low geographic variation (Isler et al 1998(Isler et al , 2001(Isler et al , 2005Zimmer and Isler 2003).…”

“…There is growing support for the idea that antbirds, and all other tracheophone suboscine passerines, develop their songs without learning (Isler et al 1998(Isler et al , 2005Zimmer and Isler 2003;Remsen 2005). Even if some evidence of learning is eventually demonstrated, the structural simplicity of antbird songs, coupled with low levels of geographic variation and absence of dialects (Isler et al 1999(Isler et al , 2001(Isler et al , 2005, indicates that its influence on song structure is minor. If suboscine birds are less able to copy or recognize divergent songs, the absence of learning may directly limit hybridization (Graves 1992;Grant and Grant 1996;Seddon and Tobias 2007), and sexual selection acting on acoustic signals in allopatric populations may lead to premating isolation.…”

Song divergence at the edge of Amazonia: an empirical test of the peripatric speciation model

“…Although song‐learning may occur in the Cotingidae (Kroodsma, 2004), recent work in another suboscine family, the antbirds (Thamnophilidae), has shown close concordance between vocal and genetic geographical variation, suggesting that, in this family, song structure is an inherited rather than learned character (Brumfield, 2005; Isler, Isler & Brumfield, 2005; Remsen, 2005). Even if some evidence of learning is eventually demonstrated in the antbirds, the structural simplicity of their songs, low levels of geographical variation, and absence of dialects (Isler et al , 1999, 2001; Isler, Isler & Brumfield, 2005) all indicate that it will be much less than that found in oscines, making suboscines arguably better subjects for examining the role of song in speciation.…”

Isleria, a new genus of antwren (Aves: Passeriformes: Thamnophilidae)

“…In addition, their numerous studies of vocal variation in antbirds (e.g. Isler et al, 1997Isler et al, , 1999Isler et al, , 2001Isler et al, , 2005Isler et al, , 2007Isler & Whitney, 2011) have not only improved our understanding of species limits within the group, but have provided methodological guidelines to incorporate vocal and geographic data to better understand taxonomy, systematics, and evolutionary processes in the family (Isler, 1997;Isler et al, 1998). The Islers' enthusiasm to learn, collaborate, and share their extraordinary knowledge of bird biology has become their trademark, and made them role models for upcoming generations of ornithologists.…”